1. Field of the Invention
The present invention relates to an antenna which can cope with different frequency bands, and a portable wireless device having the same.
2. Description of the Related Art
It is necessary for recent portable wireless devices, in particular, cellular phones to cope with radio waves of different frequency bands because of diversified and multifunctional communication. For example, in Japan, the band of 800 MHz and the band of 2 GHz are allocated as communication frequency bands for cellular phones, and when a communication carrier which provides a cellular phone communication service uses both the frequency bands for communications, a cellular phone must have antennas coping with the respective frequency bands. Meanwhile, there are cellular phones which have a function of receiving a radio wave used for a PHS (Personal Handy-phone System), a radio wave used for the Bluetooth (registered trademark) or the like, and have a function of transmitting/receiving a radio wave of a TV signal, a radio wave of a radio signal, a radio wave of a GPS (Global Positioning System) signal or the like, and such cellular phones must have antennas corresponding to the respective added functions.
It is desirable that a portable wireless device which transmits and receives radio waves of different frequency bands should have antenna elements of the respective frequency bands connected to a circuit board through a common terminal from the standpoint of the limitation of the wiring patterning of the circuit board, i.e., it is desirable that the portable wireless device should have a dual-band antenna or the like. Unexamined Japanese Patent Application KOKAI Publication No. 2002-64329 discloses plural types of antennas formed of a conductive pattern, as dual-band antennas.
One of the antennas is a meander line antenna (8) which has two meander line sections (8A, 8B), which have different meander intervals, formed in series on the internal surface of a flipper attached free to open or close to the body of a cellular phone, with the end portion of a first meander line section (8A) whose meander interval is broader connected to a circuit board. This meander line antenna (8) has electrical lengths and meander patterns set for the first meander line section (8A) and for the second meander line section (8B) respectively, such that the first meander line section (8A) and the second meander line section (8B) function as antenna in the band of 800 MHz, and such that only the first meander line section (8A) functions as antenna in the band of 1.9 GHz.
The other one of the antennas is an antenna (21) which has a ¼-wavelength antenna element (21A) coping with the 800 MHz band and a ¼-wavelength antenna element (21B) coping with the 1.9 GHz band formed in parallel on the internal surface of the flipper, with the end portion of the antenna element (21A) and the end portion of the antenna element (21B) connected to a circuit board to be simultaneously supplied with power.
Unexamined Japanese Patent Application KOKAI Publication No. 2005-269301 discloses an antenna formed of a metallic plate, as a dual-band antenna. This antenna has two antenna elements (a ¼-wavelength antenna element 1 coping with the 900 MHz band, and a ¼-wavelength antenna element 2 coping with the 1.8 GHz or 1.9 GHz band), each of which is formed by bending a metallic plate into a reversed-L shape such that each has a horizontal portion (1a, 2a) and a vertical portion (1b, 2b), and the two antenna elements are arranged such that the horizontal portions face each other with a predetermined gap therebetween, and such that the end portions of the vertical portions are connected in common to be simultaneously supplied with power.